This invention relates in general to a rotary position transducer and, more particularly, to a position transducer which employs a sensor and converter that indicates the absolute rotational position of an input shaft. The input shaft can be coupled to a rotary device such as the shaft of a motor or can be linked to the position of a linear displacement device such as a work table.
Absolute position transducers are known in the art and devices of the type to which this invention is addressed are disclosed in U.S. Pat. No. 4,556,886, No. 4,572,951, No. 4,604,575 and No. 4,612,503. These patents describe the sensing technique employed in both linear and rotational position detecting devices and also disclose a variable reluctance sensor that is employed. These transducers are known and widely used. A discussion of the advantages and disadvantages of various types of rotation angle detectors may be found in Pat. No. 4,604,575.
There are situations in which the transducers are employed where the environment adversely affects the electronic converter thereby reducing the life of the device and degrading its performance. In particular, there are circumstances where vibration, temperature and shock cause convertor malfunctioning and failure. The brute force technique of building these devices to withstand vibration, temperature and shock conditions is to build larger, sturdier and more expensive devices. However, the size of the device is critical for many applications. Unless the device is kept as small as possible, the circumstances in which the device can be employed will be limited.
Accordingly, it is a major purpose of this invention to provide an improved design for a position transducer so as to withstand shock, to operate in high temperature environments and to be as small in size as possible.
It is a related purpose of this invention to provide a device which will have nearly universal application.
And, it is a related purpose of this invention to provide those improved characteristics, including small size, at a reasonable cost.
Accordingly, the goal of this invention is to achieve an optimum trade-off of small size, low cost, ruggedness and ability to operate at high factory termperatures.